/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hedwig.util;

import com.google.protobuf.ByteString;
import org.apache.hedwig.protocol.PubSubProtocol.SubscriptionEvent;

/**
 * This class is used for subscriber to listen on subscription event.
 */
public interface SubscriptionListener {

    /**
     * Process an event from a subscription.
     * <p>
     * NOTE: It would be better to not run blocking operations in a
     *       listener implementation.
     * </p>
     *
     * @param topic
     *          Topic Name
     * @param subscriberId
     *          Subscriber Id
     * @param event
     *          Event tell what happened to the subscription.
     */
    public void processEvent(ByteString topic, ByteString subscriberId,
                             SubscriptionEvent event);
}
